Porous ureteral stent

ABSTRACT

In some embodiments, a stent includes an elongate member and a distal retention member. The elongate member is configured to be disposed within a ureter of a patient and has a first portion, a second portion and a plurality of beads bonded together. The plurality of beads define a plurality of spaces between the plurality of beads. The plurality of spaces are configured to allow fluid to flow from the first portion of the elongate member to the second portion of the elongate member. The distal retention member is configured to help maintain a portion of the stent within a kidney of the patient.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims priority to, U.S.patent application Ser. No. 13/488,075, filed on Jun. 4, 2012, entitled“POROUS URETERAL STENT”, which is a continuation of U.S. patentapplication Ser. No. 12/567,367, filed on Sep. 25, 2009, entitled“POROUS URETERAL STENT”, now U.S. Pat. No. 8,414,656, which claimspriority to U.S. Provisional Patent Application No. 61/120,109, filed onDec. 5, 2008, entitled “POROUS URETERAL STENT”, the disclosures of whichare hereby incorporated by reference in their entirety.

BACKGROUND

The invention relates generally to a medical implant and moreparticularly to a stent configured to be implanted within a ureter of apatient.

A ureter is a tubular passageway in a body that carries urine from akidney to a bladder. Ureteral stents are used to assist drainage ofurine and/or other fluids from the kidney to the urinary bladder inpatients with a ureteral obstruction and/or injury; or to protect theintegrity of the ureter during a variety of surgical manipulations.Stents may be used to treat and/or avoid ureteral obstructions (such asureteral stones or ureteral tumors), which disrupt the flow of urinefrom the kidneys to the bladder. Serious obstructions may cause urine toback up into the kidneys. Ureteral stents may also be used afterendoscopic inspection of the ureter to prevent obstruction of the ureterby swelling of the ureteral wall caused by the surgical procedure.Ureteral stents typically are tubular in shape and terminate in twoopposing ends: a kidney-end and a bladder-end.

Known stents, typically include a lumen extending through a tubularpassageway. Such known stents, however, do not allow for maximumdrainage from the kidney to the bladder. Additionally, known stents aretypically rigid to allow for easy placement in a ureter of a patient.Such rigidity, however, can cause patient discomfort and can make thestent more difficult to remove.

A need exists for a stent that provides increased drainage of urine fromthe kidney to the bladder of a patient. Further, a need exists for astent that is sufficiently rigid when inserted but causes less patientdiscomfort after implementation and is easily removable.

SUMMARY

In some embodiments, a stent includes an elongate member and a distalretention member. The elongate member is configured to be disposedwithin a ureter of a patient and has a first portion, a second portionand a plurality of beads bonded together. The plurality of beads definea plurality of spaces between the plurality of beads. The plurality ofspaces are configured to allow fluid to flow from the first portion ofthe elongate member to the second portion of the elongate member. Thedistal retention member is configured to help maintain a portion of thestent within a kidney of the patient. In some embodiments, the elongatemember defines a longitudinal axis and the plurality of spaces areconfigured to allow fluid to flow in a direction substantially normal tothe longitudinal axis.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a stent according to anembodiment.

FIG. 2 is a front view of a stent according to an embodiment.

FIG. 3 is a cross-sectional view of the stent shown in FIG. 2, takenalong line X-X in FIG. 2.

FIG. 4 is a front view of a stent according to an embodiment.

FIG. 5 is a cross-sectional view of the stent shown in FIG. 4, takenalong line S-S in FIG. 4.

FIG. 6 is a front view of a stent according to an embodiment.

FIG. 7 is a front view of a stent according to an embodiment.

FIG. 8 is a cross-sectional view of the stent shown in FIG. 7, takenalong line Z-Z in FIG. 7.

FIG. 9 a is a top view of a bead used in the stent shown in FIG. 7.

FIG. 9 b is a side view of the bead of FIG. 9 a.

FIG. 9 c-e are top views of beads according to other embodiments.

FIG. 10 is a front view of a stent according to an embodiment in a firstconfiguration.

FIG. 11 is a front view of the stent shown in FIG. 10 in a secondconfiguration.

FIG. 12 is a front view of a stent according to an embodiment in a firstconfiguration.

FIG. 13 is a front view of the stent shown in FIG. 12 in a secondconfiguration.

FIG. 14 is a cross-sectional view of the stent shown in FIG. 12 in thefirst configuration, taken along the line Y-Y in FIG. 12.

FIG. 15 is a cross-sectional view of the stent shown in FIG. 12 in thesecond configuration, taken along the line T-T in FIG. 13.

FIG. 16 is a front view of a stent according to an embodiment.

DETAILED DESCRIPTION

In some embodiments, a stent includes an elongate member and a distalretention member. The elongate member is configured to be disposedwithin a ureter of a patient and has a first portion, a second portionand a plurality of beads bonded together. The plurality of beads definea plurality of spaces between the plurality of beads. The plurality ofspaces are configured to allow fluid to flow from the first portion ofthe elongate member to the second portion of the elongate member. Thedistal retention member is configured to help maintain a portion of thestent within a kidney of the patient.

In some embodiments, a stent includes an elongate member having a distalend portion, a proximal end portion and a plurality of beads. Theelongate member defines a longitudinal axis. Each bead of the pluralityof beads has a first portion and a second portion. The first portion ofeach bead of the plurality of beads defines a lumen. The lumens of thefirst portion of each bead of the plurality of beads are substantiallyaligned along the longitudinal axis such that the lumen defined by thefirst portion of a first bead of the plurality of beads is disposedadjacent to and is in fluid communication with the lumen defined by thefirst portion of a second bead of the plurality of beads. The secondportion of the first bead of the plurality of beads is offset from thesecond portion of the second bead of the plurality of beads.

In some embodiments, a stent includes an elongate member configured toextend from a kidney to a bladder of a patient. The elongate memberincludes a first material and a second material. The second material isinterspersed within the first material and is configured to dissolvewhen the stent is disposed within a urinary tract of the patient for apredetermined amount of time. In such an embodiment, the stent is softerafter the second material dissolves.

The words “proximal” and “distal” refer to direction closer to and awayfrom, respectively, an operator (e.g., surgeon, physician, nurse,technician, etc.) who would insert the stent into the patient. Thus, forexample, the end of the stent first inserted inside the patient's bodywould be the distal end of the stent, while the end of the stent toenter the patient's body last would be the proximal end of the stent.

FIG. 1 is a schematic illustration of a stent 100 according to anembodiment. Stent 100 includes a retention member 110 and an elongatemember 150. The elongate member 150 of the stent 100 defines alongitudinal axis A_(L). The elongate member 150 of the stent 100includes a distal end portion 154, a proximal end portion 155, a firstportion 158, a second portion 156 and a plurality of beads 160 thatdefine a plurality of spaces 170. The elongate member 150 of the stent100 is configured to be disposed within a ureter of a patient. In someembodiments, the stent 100 is configured to provide support to theureter of the patient. In some embodiments, the first portion 158 of theelongate member 150 is located at the distal end portion 154 of theelongate member 150. In some embodiments, the second portion 156 of theelongate member 150 is located at the proximal end portion 155 of theelongate member 150.

Each bead of the plurality of beads 160 can be any suitable shape. Insome embodiments, the plurality of beads 160 are substantiallyspherical, figure-eight shaped, and/or the like. In some embodiments,each bead of the plurality of beads 160 has a relatively large surfacearea with rounded comers. The relatively large surface area of each beadof the plurality of beads 160 increases the area defined by theplurality of spaces 170 between the plurality of beads 160, as furtherdescribed herein. The rounded comers of the beads reduces the irritationand/or damage the stent 100 can potentially cause to the ureter of thepatient.

The plurality of beads 160 can be constructed of any suitablebiocompatible material. In some embodiments, the plurality of beads 160are constructed of thermal elastic plastic.

Each bead of the plurality of beads 160 is configured to be coupled toadjacent beads of the plurality of beads 160. In this manner, theplurality of beads 160 are coupled together to form the elongate member150. The elongate member 150 is substantially cylindrical. In otherembodiments, the plurality of beads can be coupled together to form anelongate member of any suitable shape.

Each bead of the plurality of beads 160 can be coupled to adjacent beadsof the plurality of beads 160 by any suitable means. In someembodiments, each bead of the plurality of beads 160 is melted toadjacent beads. In other embodiments, each bead of the plurality ofbeads is coupled to adjacent beads by an adhesive, a weld, or the like.

The plurality of beads 160 are coupled to each other such that aplurality of spaces 170 are defined between the plurality of beads 160.The plurality of spaces 170 are configured to allow fluid to flow in adirection substantially parallel to the longitudinal axis A_(L) from thefirst portion 158 of the elongate member 150 to the second portion 156of the elongate member 150, as described in further detail herein.Further, the plurality of spaces 170 are configured to allow fluid toflow in a direction substantially normal to the longitudinal axis A_(L).Thus, the stent has little resistance to urine flow between theplurality of spaces 170 of the elongate member 150 and the areasurrounding the elongate member 150.

The retention member 110 of the stent 100 is coupled to the distal endportion 154 of the elongate member 150 and is configured to help retaina portion of the stent 100 in a kidney of a patient when the stent 100is placed within a urinary tract of a patient. The retention member 110is also configured to help prevent the proximal migration of the stent100 when the stent 100 is placed within the urinary tract of the patientwith the retention member 110 disposed in the kidney of the patient. Inthis manner, the retention member 110 is configured to help retain theelongate member 150 in a ureter of the patient.

The retention member 110 can be any shape sufficient to prevent theproximal migration of the stent 100 when placed within the urinary tractof the patient. The retention member 110 can be, for example, anelongate member coiled in a pigtail or J-shape. In other embodiments,the retention member includes protrusions coupled to the distal endportion of the elongate member that extend in a direction substantiallynormal to the longitudinal axis A_(L). In still other embodiments, theretention member includes a malicot coupled to the distal end portion ofthe elongate member.

In some embodiments, the stent includes a second retention membersimilar to the retention member 110. The second retention member can becoupled to the proximal end portion of the elongate member. In someembodiments, the second retention member is disposed within the bladderof the patient when the stent is placed within the urinary tract of thepatient. In this manner, the second retention member can help preventdistal migration of the stent when the stent is placed within theurinary tract of the patient with the second retention member disposedin the bladder.

In use, the stent 100 is inserted into the urinary tract of a patient.In some embodiments, the stent 100 can be inserted into the urinarytract using a delivery sheath or the like. The stent 100 is placedwithin the urinary tract such that the retention member 110 is disposedwithin the kidney of the patient and the elongate member 150 extendsfrom the kidney of the patient to the bladder of the patient. When urineis in the kidney of the patient, the urine can flow through theplurality of spaces 170 defined by the plurality of beads 160 from thefirst portion 158 of the elongate member 150 to the second portion 156of the elongate member 150 and into the bladder of the patient.

While FIG. 1 shows the entire elongate member 150 constructed of aplurality of beads 160, in some embodiments, only a portion of theelongate member is constructed of a plurality of beads. For example, insome embodiments, the distal end portion and/or the proximal end portionof the stent can be solid. Said another way, the distal end portionand/or the proximal end portion of the stent can be devoid of aplurality of lumens.

In some embodiments, some and/or all of the plurality of beads include atherapeutic agent. The therapeutic agent can be configured to promotewound healing when the stent is disposed adjacent a wound. In someembodiments, the therapeutic agent is configured to dissolve and enterthe urine stream when the stent is disposed within the urinary tract ofa patient. In this manner, the therapeutic agent can promote woundhealing and/or induce other desired effects on a portion of a body of apatient that is not directly in contact with the elongate member. Inother embodiments, some and/or all of the plurality of beads areconfigured to generate oxygen when exposed to the urine of a patient.

FIGS. 2 and 3 show a stent 200 according to an embodiment. Stent 200includes a distal retention member 210, a proximal retention member 220and an elongate member 250. The elongate member 250 of the stent 200defines a longitudinal axis A1. The elongate member 250 of the stent 200includes a first portion 258, a second portion 259, a distal end portion254, a proximal end portion 256 and a plurality of beads 260 that definea plurality of spaces 270. The elongate member 250 of the stent 200 isconfigured to be disposed within a ureter of a patient. In someembodiments, the elongate member 250 is configured to provide support tothe ureter of the patient. In some embodiments, the first portion 258 ofthe elongate member 250 is located at the distal end portion 254 of theelongate member 250, and the second portion 259 of the elongate member250 is located at the proximal end portion 256 of the elongate member250.

Each bead of the plurality of beads 260 is spherically shaped. Becausethe plurality of beads 260 are spherically shaped, each bead of theplurality of beads 260 has a relatively large surface area and does notinclude sharp comers. The relatively large surface area of the pluralityof beads 260 increases the size of the plurality of spaces 270 betweenthe plurality of beads 260. Additionally, the rounded comers of theplurality of beads 260 reduces the irritation and/or damage the stent200 can potentially cause to the ureter of the patient.

The plurality of beads 260 can be constructed of any suitablebiocompatible material. In some embodiments, for example, the pluralityof beads 260 can be constructed of a thermal elastic plastic.

Each bead of the plurality of beads 260 is configured to be coupled toadjacent beads of the plurality of beads 260. In this manner, theplurality of beads 260 are coupled together to form the elongate member250. The elongate member 250 is substantially cylindrical. In otherembodiments, the plurality of beads are coupled together to form anelongate member of any suitable shape.

Each bead of the plurality of beads 260 can be coupled to adjacent beadsof the plurality of beads 260 by any suitable means. In someembodiments, each bead of the plurality of beads 260 is melted toadjacent beads. In other embodiments, each bead of the plurality ofbeads is coupled to adjacent beads by an adhesive, a weld, and/or thelike.

The plurality of beads 260 are coupled to each other such that theplurality of spaces 270 are defined between the plurality of beads 260.The plurality of spaces 270 are configured to allow fluid to flow in adirection substantially parallel to the longitudinal axis A_(L) from thefirst portion 258 of the elongate member 250 to the second portion 259of the elongate member 250, as described in further detail herein.Further, the plurality of spaces 270 are configured to allow fluid toflow in a direction substantially normal to the longitudinal axis A_(L).Thus the stent has little resistance to urine flow between the pluralityof spaces 270 of the elongate member 250 and the area surrounding theelongate member 250.

The distal retention member 210 is coupled to the distal end portion 254of the elongate member 250 and includes a plurality of beads 215structurally and functionally similar to the plurality of beads 260 ofthe elongate member 250. Each bead of the plurality of beads 215 isspherically shaped and configured to be coupled to adjacent beads of theplurality of beads 215. In this manner, the plurality of beads 215 arecoupled together to form the distal retention member 210.

The plurality of beads 215 of the distal retention member 210 arecoupled to each other such that a plurality of spaces 217 are definedbetween the plurality of beads 215. The plurality of spaces 217 areconfigured to allow fluid to flow between the plurality of beads 215.This allows fluid to flow between the kidney and the elongate member 250when the stent 200 is disposed within the urinary tract of the patient.

The distal retention member 210 has a pigtail shape. The pigtail shapeof the distal retention member 210 is configured to help retain aportion of the stent 200 in a kidney of a patient when the stent 200 isplaced within a urinary tract of a patient. The distal retention member210 is configured to help prevent proximal migration of the stent 200when the stent 200 is disposed within the urinary tract of the patientwith the distal retention member 210 disposed in the kidney of thepatient. In this manner, the distal retention member 210 is configuredto help retain the elongate member 250 in a ureter of a patient.

While the distal retention member 210 is shown having a pigtail shape,the distal retention member 210 can be any shape sufficient to preventthe proximal migration of the stent 200 when placed within the urinarytract of the patient. In some embodiments, the distal retention memberis an elongate member coiled in a J-shape. In other embodiments, thedistal retention member includes protrusions coupled to the distal endportion of the elongate member that extend in a direction substantiallynormal to the longitudinal axis A_(L). In still other embodiments, thedistal retention member includes a malicot coupled to the distal endportion of the elongate member.

The proximal retention member 220 is coupled to the proximal end portion254 of the elongate member 250 and includes a plurality of beads 225structurally and functionally similar to the plurality of beads 260 ofthe elongate member 250 and the plurality of beads 215 of the distalretention member 210. Each bead of the plurality of beads 225 isspherically shaped and configured to be coupled to adjacent beads of theplurality of beads 225. In this manner, the plurality of beads 225 arecoupled together to form the proximal retention member 220.

The plurality of beads 225 of the proximal retention member 220 arecoupled to each other such that a plurality of spaces 227 are definedbetween the plurality of beads 225. The plurality of spaces 227 areconfigured to allow fluid to flow between the plurality of beads 225.This allows fluid to flow between the elongate member 250 and a bladderof a patent when the stent 200 is disposed within the ureteral tract ofa patient.

The proximal retention member 220 has a pigtail shape. The pigtail shapeof the proximal retention member 220 is configured to help retain aportion of the stent 200 in a bladder of a patient when the stent 200 isplaced within a urinary tract of a patient. The proximal retentionmember 220 is configured to prevent distal migration of the stent 200when the stent 200 is placed within the urinary tract of the patientwith the proximal retention member 220 disposed in the kidney of thepatient. In this manner, the proximal retention member 220 is configuredto help retain the elongate member 250 in a ureter of a patient.

While the proximal retention member 220 is shown having a pigtail shape,the proximal retention member 220 can be any shape sufficient to preventthe distal migration of the stent 200 when placed within the urinarytract of the patient. In some embodiments, the proximal retention memberis an elongate member coiled in a J-shape. In other embodiments, theproximal retention member includes protrusions coupled to the proximalend portion of the elongate member that extend in a directionsubstantially normal to the longitudinal axis A_(L). In still otherembodiments, the proximal retention member includes a malicot coupled tothe proximal end portion of the elongate member.

In use, the stent 200 is inserted into the urinary tract of a patient.In some embodiments, the stent 200 is inserted into the urinary tractusing a delivery sheath or the like. The stent 200 is placed within theurinary tract such that the distal retention member 210 is disposedwithin the kidney of the patient, the proximal retention member 220 isdisposed within the bladder of the patient, and the elongate member 250extends from the kidney of the patient to the bladder of the patient.When urine is in the kidney of the patient, the urine can flow throughthe plurality of spaces 270 defined by the plurality of beads 260 fromthe first portion 258 of the elongate member 250 to the second portion259 of the elongate member 250 and into the bladder of the patient.

While FIG. 2 shows the entire stent 200 constructed of beads, in someembodiments, only a portion of a stent is constructed of beads. Forexample, FIG. 6 shows a stent 300 having an elongate member 350constructed of a plurality of beads 360, a solid distal retention member310 and a solid proximal retention member 320. The stent 300 is similarto the stent 200.

The plurality of beads 370 of the stent 300 are coupled together anddefine a plurality of spaces 370 between them. The plurality of spaces370 are configured to allow fluid to flow in a direction substantiallyparallel to a longitudinal axis A_(L) from a distal end portion 354 ofthe elongate member 350 to a proximal end portion 356 of the elongatemember 350. Further, the plurality of spaces 370 are configured to allowfluid to flow in a direction substantially normal to the longitudinalaxis A_(L). Thus, there is little resistance to urine flow between theplurality of spaces 370 of the elongate member 350 and the areasurrounding the elongate member 350.

The distal retention member 310 of the stent 300 is solid. Said anotherway, the distal retention member 310 does not include a plurality ofbeads and/or a plurality of spaces. Having a solid distal retentionmember 310 can increase the rigidity of the distal retention member 310.Thus, the distal retention member 310 can provide better retentionwithin a kidney of a patient.

The proximal retention member 320 of the stent 300 is also solid. Saidanother way, the proximal retention member 320 does not include aplurality of beads and/or a plurality of spaces. Having a solid proximalretention member 320 can increase the rigidity of the proximal retentionmember 320. Thus, the proximal retention member 320 can provide betterretention within a bladder of a patient.

FIG. 3 is a cross-sectional view of the stent 200, taken along line X-Xin FIG. 2. FIG. 3 shows the plurality of beads 260 coupled together anddefining the plurality of spaces 270. As stated above, urine isconfigured to flow between the plurality of spaces 270 when the stent200 is disposed within a urinary tract of a patient.

FIG. 4 is a front view of a stent 800 according to an embodiment. FIG. 5is a cross-sectional view of the stent 800, taken along line S-S in FIG.4. The stent 800 is similar to stent 200 and has an elongate member 850,a proximal retention member 820 and a distal-retention member 810. Theproximal retention member 820 is coupled to a proximal end portion 856of the elongate member 850 and the distal retention member 810 iscoupled to a distal end portion 854 of the elongate member 850.

The elongate member 850 of the stent 800 includes a plurality of beads860 that define a plurality of spaces 870. The plurality of beads 860 ofthe elongate member 850 further define an inner lumen 880 (see e.g.,FIG. 5). The plurality of spaces 870 defined by the plurality of beads860 of the stent 800 are configured to allow fluid to flow from thedistal end portion 854 of the elongate member 850 to the proximal endportion 856 of the elongate member 850. The inner lumen 880 defined bythe elongate member 850 is configured to allow fluid to flow from thedistal end portion 854 of the elongate member 850 to the proximal endportion 856 of the elongate member 850. Because the size of the innerlumen 880 is greater than the size of the plurality of spaces 870, agreater rate of fluid may flow from the kidney to the bladder of thepatient when the stent 800 is placed within the urinary tract of apatient. Additionally, the inner lumen 880 is in fluidic communicationwith the area surrounding the elongate member 850 via the plurality ofspaces 870. This allows fluid to flow between the area surrounding theelongate member 850 and the inner lumen 880.

In use, the stent 800 is inserted into the urinary tract of a patient.While the stent 200 can be inserted into the urinary tract using adelivery sheath or the like, because the stent 800 defines an innerlumen 880 the stent 800 can also be inserted into the urinary tractusing a guide wire threaded through the inner lumen 880.

The stent 800 is placed within the urinary tract such that the distalretention member 810 is disposed within the kidney of the patient, theproximal retention member 820 is disposed within the bladder of thepatient, and the elongate member 850 extends from the kidney of thepatient to the bladder of the patient. When the stent 800 is placedwithin the urinary tract, urine can flow from the kidney, through theinner lumen 880 and/or the plurality of spaces 870 defined by theplurality of beads 860, and into the bladder of the patient.

FIGS. 7-8 show a stent 400 according to an embodiment. The stent 400 issimilar to the stent 300 and includes an elongate member 450, a proximalretention member 420, and a distal retention member 410. The elongatemember 450 of the stent 400 includes a distal end portion 454, aproximal end portion 456 and a plurality of beads.

FIGS. 9 a-9 b show a single bead 460 of the plurality of beads of thestent 400. Each bead 460 of the plurality of beads includes a firstportion 462 and a second portion 466. The first portion 462 issubstantially circular in shape and defines a lumen 463. The lumen 463is configured to allow a liquid to flow through it. The lumen 463defined by the first portion 462 is configured to be aligned with thelumen defined by the first portion of each of the plurality of beads, asdescribed in further detail herein (see e.g., FIG. 8). Further, thefirst portion 462 of the bead 460 is configured to be coupled to thefirst portion of each adjacent bead of the plurality of beads, asdescribed in further detail herein.

The second portion 466 of the bead 460 is substantially circular inshape and defines a lumen 467. The lumen 467 defined by the secondportion 466 is configured to be offset from the lumen defined by thesecond portion of each bead of the plurality of beads disposed adjacentthe bead 460 when the plurality of beads are stacked together as shownin FIGS. 7 and 8, and as described in further detail herein. Further,the second portion 466 of the bead 460 is configured to be spaced apartfrom the second portion of each bead disposed adjacent the bead 460 whenthe plurality of beads are stacked together, as described in furtherdetail herein. As shown in FIG. 9 b, the second portion 466 of the bead460 has a width that is less than a width of the first portion 462 ofthe bead 460. The first portion 462 of the bead 460 and the secondportion 466 of the bead 460 are arranged such that the bead 460 issubstantially “figure 8” shaped.

As shown in FIGS. 7 and 8, the plurality of beads are coupled togetherto form the stent 400. The first portion 462 of a first bead 460 of theplurality of beads is coupled to the first portion 472 of a second bead470 of the plurality of beads. The second bead 470 of the plurality ofbeads is substantially similar to the first bead 460 and is disposedadjacent the first bead 460. The lumen 463 defined by the first portion462 of the first bead 460 is aligned and in fluid communication with thelumen 473 defined by the first portion 472 of the second bead 470.

The second portion 466 of the first bead 460 is offset from the secondportion 476 of the second bead 470. Said another way, the lumen 467defined by the second portion 466 of the first bead 460 is not alignedwith the lumen 477 defined by the second portion 476 of the second bead470. Further, the second portion 466 of the first bead 460 is not incontact with the second portion 476 of the second bead 470. Therefore,the second portion 466 of the first bead 460 and the second portion 476of the second bead 470 define a space between them. As shown in FIGS. 7and 8, additional beads are coupled to the first bead 460 and the secondbead 470 in the manner described above. In this manner, the stent 400 isformed. In other embodiments, the lumen defined by the second portion ofthe first bead is partially aligned with the lumen defined by the secondportion of the second bead.

The distal retention member 410 of the stent 400 is solid and is coupledto the distal end portion 454 of the elongate member 450. The distalretention member 410 does not include a plurality of beads and/or aplurality of spaces. Having a solid distal retention member 410 canincrease the rigidity of the distal retention member 410. Thus, thedistal retention member 410 can provide better retention within a kidneyof a patient. In other embodiments, the distal retention member of thestent includes a plurality of beads, similar to the bead 460.

The proximal retention member 420 of the stent 400 is solid and iscoupled to the proximal end portion 456 of the elongate member 450. Theproximal retention member 420 does not include a plurality of beadsand/or a plurality of spaces. Having a solid proximal retention member420 can increase the rigidity of the proximal retention member 420.Thus, the proximal retention member 420 can provide better retentionwithin a bladder of a patient. In other embodiments, the distalretention member of the stent includes a plurality of beads, similar tothe bead 460.

In use, the stent 400 is inserted into the urinary tract of a patient.For example, the stent 400 can be inserted into the urinary tract usinga delivery sheath, a guide wire, and/or the like. Once disposed withinthe urinary tract of the patient, urine is configured to flow throughthe lumens defined by the first portions of the plurality of beads froma kidney to a bladder of the patient. Urine is also configured to flowthrough the lumens defined by the second portions of the plurality ofbeads and the spacing between the second portions of the plurality ofbeads.

In one embodiment, when the stent 400 is disposed within the urinarytract of the patient, the second portion of each of the plurality ofbeads contacts the ureter of the patient. For example, the secondportion 466 of the first bead 460 of the plurality of beads and thesecond portion 476 of the second bead 470 of the plurality of beadscontact the ureter of the patient. In this manner, the stent 400 helpssupport the ureter of the patient.

In some embodiments, because the second portion of each of the pluralityof beads is offset from and does not contact the second portion ofadjacent beads, the elongate member 450 minimally contacts the ureter ofa patient. This can decrease the irritation and/or discomfort thepatient feels when the stent 400 is disposed within the urinary tract ofthe patient.

In some embodiments, the first portion of each bead has a width that isless than or smaller than the width of the second portion of each bead.Thus, when assembled, the second portion of each bead of the pluralityof beads is coupled to the second portion of the beads adjacent eachbead and the first portion of each bead of the plurality of beads can bespaced apart from the first portion of the beads adjacent each bead.

In further embodiments, a first portion of one bead has a width that isgreater than the width of the second portion of the bead, while a firstportion of another bead has a width that is smaller than the width ofthe second portion of that another bead. In such an embodiment, firstportions and/or second portions of adjacent beads may be fused orcoupled together. For example, a first portion of a first bead may becoupled to a first portion of a second bead and a second portion of thefirst bead may be coupled to a second portion of a third bead.

While FIGS. 7-9 b show a substantially “figure 8” shaped bead 460, inother embodiments, the bead can be any suitable shape. FIGS. 9 c-9 eshow various beads that can be used to construct a stent similar to thestent 400 described above. For example, FIG. 9 c shows an oval shapedbead 960 defining a first lumen 963 and a second lumen 967. The firstlumen 963 is configured to allow a liquid, such as urine, to flowthrough it. The first lumen 963 is configured to be aligned with thefirst lumen defined by each bead used to construct the stent. In thismanner, liquid can flow from a kidney of a patient to a bladder of apatient when the stent is disposed within a ureter of a patient. Thesecond lumen 967 can be offset from the second lumen defined by eachbead disposed adjacent the bead 960 when the beads are stacked orcoupled together to form the stent.

FIG. 9 d shows an oval shaped bead 1060 defining a first lumen 1063, asecond lumen 1067, and a third lumen 1065. The second lumen 1067 isconfigured to allow a liquid, such as urine, to flow through it. Thesecond lumen 1067 is configured to be aligned with the second lumendefined by each bead used to construct the stent. In this manner, liquidcan flow from a kidney of a patient to a bladder of a patient when thestent is disposed within a ureter of a patient. The first lumen 1063 andthe third lumen 1065 can be offset from the first lumen and the thirdlumen defined by each bead disposed adjacent the bead 1060,respectively, when the beads are stacked together to from the stent. Inother embodiments, the first lumen or the third lumen can be alignedwith the first lumen or the third lumen defined by each bead used toconstruct the stent, respectively. In such embodiments, the second lumencan be offset from the second lumen defined by each bead disposedadjacent the bead when the beads are stacked or coupled together to formthe stent.

FIG. 9 e shows a substantially cross shaped bead 1160 having a pluralityof legs 1165 and defining a middle lumen 1163. The each leg of theplurality of legs 1165 defines a lumen 1167. The middle lumen 1163defined by the bead 1160 is configured to allow liquid, such as urine,to flow through it. In this manner, liquid can flow from a kidney of apatient to a bladder of a patient when the stent is disposed within aureter of a patient. The middle lumen 1163 is also configured to bealigned with the middle lumen defined by each bead used to construct thestent. The lumens 1167 defined by the plurality of legs 1165 areconfigured to be offset from the lumens defined by the plurality of legsof each bead disposed adjacent the bead 1160 when the beads are stackedor coupled together to form the stent.

FIGS. 10 and 11 show a stent 700 according to an embodiment. The stent700 includes a distal retention member 710, a proximal retention member720 and an elongate member 750. The stent 700 has a first configuration(FIG. 10) and a second configuration (FIG. 11). The elongate member 750of the stent 700 has a distal end portion 754, and a proximal endportion 756. The elongate member 750 is configured to be disposed withina ureter of a patient and can provide support to the ureter of thepatient. In some embodiments, the elongate member defines a lumenthrough which urine can flow when the elongate member is disposed withina ureter of a patient.

The stent 700, including the distal retention member 710, the proximalretention member 720 and the elongate member 750, is constructed of afirst material 760 and a second material 770. As shown in FIG. 10, thesecond material 770 is interspersed within the first material 760. Forexample, the second material 770 can be interspersed within the firstmaterial 760 in spherical portions. The portions of the second material770 are nonuniformly interspersed within the first material 760 suchthat when the second material 770 dissolves, as further describedherein, a plurality of spaces 772 are created. The plurality of spaces772 allow fluid to flow from a distal end portion 754 of the elongatemember 750 to a proximal end portion 756 of the elongate member 750. Inother embodiments, the portions of the second material have shapes otherthan spheres. In still other embodiments, the portions of the secondmaterial are uniformly spaced apart from each other.

The second material 770 is highly soluble in aqueous solutions. In someembodiments, for example, the second material 770 can be formed of acrystallized salt. The crystallized salt can be inorganic and/or organicsalt. For example, the salt can be sodium chloride, sodium acetateand/or sodium citrate. Because the second material 770 is highly solublein aqueous solutions, the second material 770 is configured to dissolvewhen the stent 700 is placed within an aqueous solution.

After the second material 770 dissolves, a plurality of spaces 772 aredefined by the first material 760. The plurality of spaces 772 aredefined or located where the second material 770 was located prior todissolving. The plurality of spaces 772 cause the stent 700 to be softerthan the stent 700 prior to the second material 770 dissolving. Theamount the stent 700 softens when placed within an aqueous solution canbe varied by varying the amount of second material 770 in the stent 700.The greater the amount of second material 770 included in the stent 700,the softer the stent 700 will become when the second material 770dissolves. The softness of the stent 700 may also vary with the softnessof the first material 760.

The first material 760 can be a thermal elastic polymer such as EVA orPercuflex polymers as sold by Boston Scientific. The first material 760is configured to remain solid and not dissolve when the second material770 dissolves.

Prior to being inserted into a body of a patient, the stent 700 isplaced within an aqueous solution. This causes the second material 770to dissolve, leaving the plurality of spaces 772 and moving the stent700 from its first configuration (FIG. 10) to its second configuration(FIG. 11). When in its second configuration, each space of the pluralityof spaces 772 can be in fluid communication with other spaces of theplurality of spaces 772. In this manner, fluid is configured to flowthrough the plurality of spaces 772 from the distal end portion 754 ofthe elongate member 750 to the proximal end portion 756 of the elongatemember. Additionally, as shown in FIG. 11, the distal retention member710 and the proximal retention member 720 retain their pigtail shapewhen the stent 700 is in the second configuration.

In use, the stent 700 is inserted into the urinary tract of a patient.In some embodiments, the stent 700 can be inserted into the urinarytract using a delivery sheath or the like. The stent 700 is placedwithin the urinary tract such that the distal retention member 710 isdisposed within the kidney of the patient, the proximal retention member720 is disposed within the bladder of the patient, and the elongatemember 750 extends from the kidney of the patient to the bladder of thepatient. When urine is in the kidney of the patient, the urine can flowthrough the plurality of spaces 770 defined by the plurality of beads760 from the distal end portion 754 of the elongate member 750 to theproximal end portion 756 of the elongate member 750 and into the bladderof the patient.

FIGS. 12-15 show a stent 500 according to an embodiment. The stent 500includes a distal retention member 510, a proximal retention member 520and an elongate member 550. The stent 500 has a first configuration(FIG. 12) and a second configuration (FIG. 13). Similar to the stent 200described above, the elongate member 550 of the stent 500 is configuredto be disposed within a ureter of a patient and can provide support tothe ureter of the patient. The elongate member 550 defines a lumen 580through which urine can flow when the elongate member 550 is disposedwithin a ureter of a patient.

The stent 500, including the distal retention member 510, the proximalretention member 520 and the elongate member 550, is constructed of afirst material 560 and a second material 570. As shown in FIGS. 12 and15, the second material 570 is interspersed within the first material560. For example, the second material 570 can be interspersed within thefirst material 560 in spherical portions having diameters of about 1micron to about 200 microns. The portions of the second material 570 arenonuniformly spaced apart from each other. In other embodiments, theportions of the second material have shapes other than spheres. In stillother embodiments, the portions of the second material are uniformlyspaced apart from each other.

The second material 570 is highly soluble in aqueous solutions, such as,for example, urine. In some embodiments, for example, the secondmaterial 570 is formed of a crystallized salt. The crystallized salt canbe inorganic and/or organic salt. For example, the salt can be sodiumchloride, sodium acetate and/or sodium citrate. Salts that do not formprecipitation with calcium and/or magnesium and/or salts that do notirritate the tissue of a patient, are preferred. In other embodiments,the second material is another suitable material such as glucose, sugar,herbal extracts, and/or the like.

Because the second material 570 is highly soluble in aqueous solutions,the second material 570 is configured to dissolve over a predeterminedtime period when the stent 500 is disposed within the urinary tract of apatient. In some embodiments, for example, the second material 570dissolves in a period of between about one and four days. In otherembodiments, the second material dissolves in a period of between fourand twenty-four hours. In still other embodiments, the second materialdissolves in less than four hours. In still other embodiments, thesecond material takes more than four days to dissolve.

After the second material 570 dissolves, a plurality of spaces 572 aredefined by the first material 560. The plurality of spaces 572 aredefined or located where the second material 570 was located prior todissolving. The plurality of spaces 572 cause the stent 500 to be softerthan the stent 500 prior to the second material 570 dissolving

The first material 560 can be a thermal elastic polymer such as EVA orPercuflex polymers as sold by Boston Scientific. The first material 560is configured to remain solid when the second material 570 dissolves.The first material 560 does not dissolve when the stent 500 is placedwithin the urinary tract of a patient.

The stent 500 has a first configuration (FIG. 12) and a secondconfiguration (FIG. 13). Before the second material 570 dissolves, thestent 500 is in the first configuration. When in the firstconfiguration, the stent 500 is substantially rigid. Because the stent500 is substantially rigid in the first configuration, the stent 500 caneasily be placed within a body of a patient. Additionally, the stent 500maintains its shape when in the first configuration.

When the stent 500 is in the first configuration, the distal retentionmember 510 has a pigtail shape. The pigtail shape of the distalretention member 510 is configured to help retain a portion of the stent500 in a kidney of a patient when the stent 500 is placed within aurinary tract of a patient. The distal retention member 510 isconfigured to prevent the proximal migration of the stent 500 when thestent 500 is in the first configuration. In this manner, the distalretention member 510 is configured to help retain the elongate member550 in a ureter of a patient, when the stent 500 is in the firstconfiguration.

Similar to the distal retention member 510, when the stent 500 is in thefirst configuration, the proximal retention member 520 has a pigtailshape. The pigtail shape of the proximal retention member 520 isconfigured to help retain a portion of the stent 500 in a bladder of apatient when the stent 500 is placed within a urinary tract of apatient. The proximal retention member 520 is configured to prevent thedistal migration of the stent 500 when the stent 500 is in the firstconfiguration. In this manner, the proximal retention member 520 isconfigured to help retain the elongate member 550 in a ureter of apatient, when the stent 500 is in the first configuration.

The stent 500 is inserted into the urinary tract of a patient when inthe first configuration. Said another way, the stent 500 is insertedinto the urinary tract of the patient prior to the second material 570dissolving. In some embodiments, the stent 500 can be inserted into theurinary tract using a delivery sheath, a guide wire and/or the like. Forexample, a guide wire can be inserted through the lumen 580 defined bythe elongate member 550. The guide wire can straighten the distalretention member 510 and the proximal retention member 520 to enableinsertion of the stent 500 into the body of a patient. Alternatively, adelivery sheath can be disposed around the stent 500 and can beconfigured to straighten the distal retention member 510 and theproximal retention member 520.

The stent 500 is placed within the urinary tract such that the distalretention member 510 is disposed within the kidney of the patient, theproximal retention member 520 is disposed within the bladder of thepatient, and the elongate member 550 extends from the kidney of thepatient to the bladder of the patient. Once the guide wire and/or thedelivery sheath is removed, the distal retention member 510 and theproximal retention member 520 regain their shape as shown in FIG. 12.When urine is in the kidney of the patient, the urine can flow throughthe lumen 580 defined by the elongate member 550, from the distal endportion 554 of the elongate member 550 to the proximal end portion 556of the elongate member 550, and into the bladder of the patient.

The stent 500 moves from the first configuration (FIG. 12) to the secondconfiguration (FIG. 13) when the second material 570 dissolves andcreates the plurality of spaces 572 in the stent 500. In the secondconfiguration, the stent 500 becomes soft and the distal retentionmember 510 and the proximal retention member 520 become flexible andlose their biasing. In some embodiments, the distal retention member 510and the proximal retention member 520 define axes that are substantiallycollinear with an axis defined by the elongate member 550 when the stent500 is in the second configuration.

When the stent 500 is placed within the urinary tract of the patient,the second material 570 is exposed to urine that flows from the kidneyof the patient to the bladder of the patient and after a predeterminedtime, the second material 570 dissolves. Accordingly, the stent 500moves from the first configuration (FIG. 12) to the second configuration(FIG. 13). As described above, when the stent 500 is in the secondconfiguration, the stent 500 softens and the distal retention member 510and the proximal retention member 520 become flexible and lose theirbiasing. When the distal retention member 510 loses its biasing, it nolonger retains a portion of the stent 500 within a kidney of a patient.Similarly, when the proximal retention member 520 loses its biasing, itno longer retains a portion of the stent 500 within a bladder of apatient. As such, the stent 500 can be easily removed from the urinarytract of the patient.

In some embodiments, the second material 570 can be configured tomaintain acidic urine and/or lower the pH of urine when dissolved withinthe urine of a patient. Lowering the pH of the urine can reduce theformation of bacterial biofilm and/or prevent encrustation of urine whenthe stent 500 is disposed within the urinary tract of a patient.

In one embodiment, the stent 500 is manufactured by adding the secondmaterial 570, to a base resin consisting of the first material 560.Depending on how soft the stent 500 is to become once the secondmaterial 570 dissolves, the amount of second material 570 added to thefirst material 560 can be varied. The greater the amount of secondmaterial 570 in the stent 500, the softer the stent 500 will becomeafter the second material 570 dissolves. Then the stent 500 is formed.The stent 500 can be formed by placing the base resin into a mold and/orthe like. Once the stent 500 is formed, it can be inserted into a bodyof a patient as described above.

In some embodiments, the first material and/or the second materialincludes a therapeutic agent. The therapeutic agent can be configured topromote wound healing when the stent is disposed adjacent a wound. Insome embodiments, the therapeutic agent is configured to dissolve andenter the urine stream when the stent is disposed within the urinarytract of a patient. In this manner, the therapeutic agent promotes woundhealing and/or induces other desired effects on a portion of a body of apatient that is not directly in contact with the elongate member. Inother embodiments, the first material and/or the second material isconfigured to generate oxygen when exposed to the urine of a patient.

While stent 500 is shown as being solid, FIG. 16 shows a stent 600according to an embodiment, that is constructed from a plurality ofbeads of a first material 660 and a plurality of beads of a secondmaterial 665. The stent 600 includes a distal retention member 610, aproximal retention member 620 and an elongate member 650. Similar to thestent 500, the stent 600 has a first configuration (FIG. 16) and asecond configuration (not shown).

The distal retention member 610 and the proximal retention member 620are configured to help retain at least a portion of the stent 600 withina kidney of a patient and within a bladder of a patient, respectively,when in the first configuration. The elongate member 650 is configuredto be disposed within the ureter of a patient.

The distal retention member 610, the proximal retention member 620 andthe elongate member 650 of the stent 600 include a plurality of beads ofa first material 660 and a plurality of beads of a second material 665.When the stent 600 is disposed within the urinary tract of a patient,the plurality of beads of the second material 665 are configured todissolve over a period of time. When the plurality of beads of thesecond material 665 dissolve, the stent 600 softens and can easily beremoved from the body of the patient.

While various embodiments have been described above, it should beunderstood that they have been presented by way of example only, and notlimitation. Where methods described above indicate certain eventsoccurring in certain order, the ordering of certain events may bemodified. Additionally, certain of the events may be performedconcurrently in a parallel process when possible, as well as performedsequentially as described above.

Although various embodiments have been described as having particularfeatures and/or combinations of components, other embodiments arepossible having a combination of any features and/or components from anyof embodiments where appropriate. For example, similar to stent 500,stent 200 can be made of two or more different materials, one of whichis configured to dissolve when the stent is placed within a ureter of apatient. Additionally, any of the embodiments described herein can beconstructed with solid retention members and/or retention membersincluding beads.

In some embodiments, a stent includes an elongate member and a distalretention member. The elongate member has a first portion, a secondportion, and a plurality of beads bonded together. The plurality ofbeads define a plurality of spaces between the plurality of beads. Theplurality of spaces are configured to allow fluid to flow from the firstportion of the elongate member to the second portion of the elongatemember. The elongate member is configured to be disposed within a ureterof a patient. The distal retention member is configured help maintain aportion of the stent within a kidney of the patient.

In some embodiments, the elongate member defines a lumen extending fromthe first portion of the elongate member to the second portion of theelongate member. In some embodiments, the plurality of beads are thermalelastic plastic beads. In some embodiments, the plurality of beads arefused together. In some embodiments, the distal retention memberincludes a plurality of beads. In some embodiments, the distal retentionmember is unitarily formed.

In some embodiments, the stent includes a proximal retention memberconfigured to help maintain a portion of the stent within a bladder ofthe patient. In some embodiments, the proximal retention member includesa plurality of beads. In some embodiments, the proximal retention memberis unitarily formed.

In some embodiments, the plurality of beads are substantially spherical.In some embodiments, at least one bead of the plurality of beadsincludes a therapeutic agent.

In some embodiments, the elongate member defines a longitudinal axis andthe plurality of spaces are configured to allow fluid to flow in adirection substantially normal to the longitudinal axis. In someembodiments, the plurality of spaces are configured to allow fluid toflow in a direction substantially normal to the longitudinal axis and ina direction substantially parallel to the longitudinal axis.

In some embodiments, a stent includes an elongate member having a distalend portion, a proximal end portion, and a plurality of beads. Theelongate member defines a longitudinal axis. Each bead of the pluralityof beads has a first portion and a second portion. The first portion ofeach of the plurality of beads defines a lumen. The lumens of the firstportions of each of the plurality of beads are substantially alignedalong the longitudinal axis such that the lumen defined by the firstportion of the first bead of the plurality of beads is in fluidcommunication with the lumen defined by the first portion of a secondbead of the plurality of beads. The second portion of the first bead ofthe plurality of beads is offset from the second portion of the secondbead of the plurality of beads.

In some embodiments, the second portion of the first bead of theplurality of beads defines a lumen. The second portion of the secondbead of the plurality of beads defines a lumen. The lumen defined by thesecond portion of the second bead is offset from the lumen defined bythe second portion of the first bead.

In some embodiments, the plurality of beads are substantially figureeight shaped. In some embodiments, at least one bead of the plurality ofbeads includes a therapeutic agent.

In some embodiments, the stent includes a proximal retention memberconfigured to help maintain a portion of the stent within a bladder of apatient. In some embodiments, the proximal retention member includes aplurality of beads. In some embodiments, the proximal retention memberis unitarily formed.

In some embodiments, the stent includes a distal retention memberconfigured to help maintain a portion of the stent within a kidney of apatient. In some embodiments, the distal retention member includes aplurality of beads. In some embodiments, the distal retention member isunitarily formed.

In some embodiments, the second portion of the first bead of theplurality of beads is coupled to the second portion of the second beadof the plurality of beads.

In some embodiments, the second portion of the first plurality of beadsdoes not contact the second portion of the second bead of the pluralityof beads. The first bead is adjacent the second bead.

In some embodiments, the first portion of the first bead of theplurality of beads is coupled to the first portion of the second bead ofthe plurality of beads.

In some embodiments, the first portion of the first bead of theplurality of beads does not contact the first portion of the second beadof the plurality of beads. The first bead is adjacent the second bead.

In some embodiments, a stent includes an elongate member configured toextend from a kidney to a bladder of a patent. The elongate memberincludes a first material and a second material. The second material isformulated to dissolve when the stent is disposed within a urinary tractof the patient for a predetermined amount of time. The stent is softerafter the second material dissolves.

In some embodiments, the second material is crystallized salt. In someembodiments, the second material has a high solubility in aqueoussolutions. In some embodiments, the second material is formulated tolower the pH of urine when dissolved within the urinary tract of thepatient. In some embodiments, the second material ix formulated topromote wound healing when dissolved adjacent to a wound of a patient.

In some embodiments, the stent includes a distal retention member havingthe first material and the second material. The distal retention memberis configured to move from a first configuration to a secondconfiguration when the stent is disposed within the urinary tract of thepatient for a predetermined amount of time. The distal retention memberis configured to help maintain a portion of the stent within the kidneyof the patient when in the first configured. The distal retention memberconfigured to allow the stent to migrate from the kidney of the patientto the bladder of the patient when in the second configuration.

In some embodiments, the first material is a thermal elastic polymer. Insome embodiments, the second material is interspersed within the firstmaterial in portions having diameters between 1-200 microns.

In some embodiments, the predetermined amount of time is between one andseven days. In some embodiments, the second material is interspersedwithin the first material before dissolving.

What is claimed is:
 1. A stent comprising: an elongate member having adistal end portion, a proximal end portion and a plurality of beads, theelongate member defining a longitudinal axis, each bead of the pluralityof beads has a first portion and a second portion, the first portion ofeach of the plurality of beads defines a lumen, the second portion thefirst bead of the plurality of beads defines a lumen and the secondportion of the second bead of the plurality of beads defines a lumen,the lumen defined by the second portion of the second bead is offsetfrom the lumen defined by the second portion of the first bead.
 2. Thestent of claim 1, wherein the plurality of beads are substantiallyfigure eight shaped.
 3. The stent of claim 1, further comprising: aproximal retention member configured to help maintain a portion of thestent within a bladder of a patient, the proximal retention memberincluding a plurality of beads.
 4. The stent of claim 1, wherein thesecond portion of the first bead of the plurality of beads does notcontact the second portion of the second bead of the plurality of beads,the first bead being adjacent the second bead.
 5. The stent of claim 1,wherein the first portion of the first bead of the plurality of beads iscoupled to the first portion of the second bead of the plurality ofbeads.
 6. The stent of claim 1, wherein the first portion of the firstbead of the plurality of beads does not contact the first portion of thesecond bead of the plurality of beads, the first bead being adjacent thesecond bead.
 7. A stent comprising: an elongate member configured toextend from a kidney to a bladder of a patient, the elongate memberincluding a first material and a second material, the second materialformulated to dissolve when the stent is disposed within a urinary tractof the patient for a predetermined amount of time, the stent beingsofter after the second material dissolves, the second material being acrystallized salt.
 8. The stent of claim 7, wherein the second materialhas a high solubility in aqueous solutions.
 9. The stent of claim 7,wherein the second material is formulated to lower the pH of urine whendissolved within the urinary tract of the patient.
 10. The stent ofclaim 7, wherein the second material is formulated to promote woundhealing when dissolved adjacent to a wound of the patient.
 11. The stentof claim 7, further comprising: a distal retention member including thefirst material and the second material, the distal retention memberconfigured to move from a first configuration to a second configurationwhen the stent is disposed within the urinary tract of the patient forthe predetermined amount of time, the distal retention member configuredto help maintain a portion of the stent within the kidney of the patientwhen in the first configuration, the distal retention member configuredto allow the stent migrate from the kidney of the patient to the bladderof the patient when in the second configuration.
 12. The stent of claim7, wherein the second material is interspersed within the first materialbefore dissolving.